English: The tetrarchs (from the Greek words for "Rulers of a quarter") were the four co-rulers that governed the Roman Empire as long as Diocletian's reform lasted. On a corner of Saint Mark's in Venice, next to the "Porta della Carta", stands a statue where they are portraied embracing, in sign of harmony: it is a porphyry sculpture dating from the 4th century, sculpted in Asia Minor. It probably originally decorated two separate pillars and were plundered by the Venetians from Constantinople.